This invention relates to automotive disc brakes, and particularly to a manually-operated means for making it easier to replace worn brake pads.
In automobiles and trucks a brake assembly is provided at each ground wheel. Quite often the front wheels are provided with disc brakes, and the rear wheels are provided with drum brakes. Sometimes disc brakes are provided on both the front wheels and the rear wheels. The present invention is concerned with a mechanism that makes it easier to replace worn brake pads on disc brakes.
A conventional disc brake assembly comprises a circular disc connected to the road wheel, and a caliper mechanism encircling an edge area of the disc at or near the twelve o'clock position. A piston-cylinder means within the caliper mechanism acts on brake pads arranged along opposite faces of the rotating disc to exert a braking force thereon when the motorist applies foot pressure to the brake pedal.
After a period of service the brake pads become worn, thereby necessitating their removal and replacement with new brake pads. One problem encountered during the brake pad-replacement operation is retraction of the associated piston into its cylinder. During service the pads become thinner; when it becomes necessary to replace the pads the piston is in an "extended" position projecting a significant distance from the associated cylinder. Before new pads can be inserted into the caliper mechanism it is necessary to forcibly retract the piston back into the cylinder (because the new pads are appreciably thicker than the worn pads, and therefore take up more axial space in the caliper mechanism). Retraction of the piston into the cylinder is made difficult because the brake fluid in the piston is in a semi-pressurized condition. Also, the piston seals offer some resistance to piston motion. Occasionally the piston-cylinder interface becomes corroded or packed with contaminants or sludge, thus posing another obstruction to retractive motion of the piston.
The present invention relates to a low cost manual mechanism that can be used to readily move a brake actuation piston from an extended position to a retracted position, to thereby facilitate the process of replacing worn brake pads with new brake pads. The manual mechanism is designed so that it can be used on a variety of different disc brake constructions, e.g. Ford, Chevrolet, Plymouth, etc.